For internal combustion engines, the engine often runs in an optimal condition at steady state. For example, when the engine is in a vehicle and the vehicle is traveling at a constant speed on a flat road. During the steady state condition, a multi-stage catalyst that receives exhaust from the engine and removes a portion of pollutants and particulate from the exhaust may perform at an optimum level or may operate within specified limits.
However, there are often conditions where the engine is in transient state, such as sudden acceleration or deceleration, encountering a hill, etc. During the transient conditions, the engine and/or catalyst may not run at optimally or may operate outside the specified limits. One reason for the decreased performance of the engine is a transport delay where an increase in fuel rate input into the engine is delayed by various components, such as a compressor and/or a charge air cooler.